This issue is a follow-on to the Problem editing the rules of a group thread. and seems to be specific to Rule Type = Group.
When you add a rule of Rule Type = Group, the left hand pane gets pre-filled with the 1st group in the drop down list. If you change the radio button from “select” to “unselect”, the left pane updates immediately. However, if you select a different group from the drop down list, the left pane does not update automatically.
You must click on a rule in the left pane in order to be sure that the pane updates and the correct group gets saved. If you add more than one rule while in this add/edit Search Rules window without clicking on the left pane, then the 1st group in the drop down list gets saved instead of the group that was ultimately chosen. Note: it appears that when only 1 rule is added, the new group seems to be updated when the record is saved.
Until this issue gets resolved, a good practice is to click each rule in the left pane to be sure that the correct details have been applied.